Catalysts for the selective conversion of straight-chain hydrocarbons

ABSTRACT

Improved catalysts for the selective conversion of straightchain hydrocarbons contained in a hydrocarbon feed comprise a synthetic, relatively small pore size crystalline aluminosilicate zeolite. Preferably, the synthetic small pore size zeolite is combined with a metallic hydrogenation component and used in the selective conversion of low octane-producing normal paraffins to upgrade the hydrocarbon feed stock. The process is preferably conducted in the presence of added hydrogen at elevated temperatures and pressures.

United States Patent Esso Research and Engineering CompanyContinuation-in-part of application Ser. No. 667,660, Sept. 14, 1967,now Patent No. 3,575,846, and a continuation-in-part of 637,911, May 12,1967, now Patent No. 3,497,448. This application Oct. 15, 1969, Ser. No.866,742

[73] Assignee [54] CATALYSTS FOR THE SELECTIVE CONVERSION OFSTRAIGHT-CHAIN HYDROCARBONS 16 Claims, No Drawings [52] U.S.Cl 208/111,

[51] lnt.Cl ..C10g37/06, C07c 3/58, BOlj 11/40 [50] Field of Search208/60,

[56] I References Cited UNITED STATES PATENTS 3,039,953 6/1962 Eng208/26 3,331,768 7/1967 Mason et al. 208/111 2,950,952 8/1960 Breck61281 23/113 3,140,322 7/1964 Frilette CI al 208/120 X 3,344,058 7/1967Miale 208/111 3,509,042 4/1970 M1818 208/120 3,294,858 12/1966 Butler eta1. 208/26 3,1 14,696 12/1963 Weisz 208/66 3,331,767 7/1967 Arey 6! a1.208/111 3,395,096 7/1968 Gladrow et al. 208/1 1 1 3,314,895 4/1967 Munns252/455 Primary Examiner-Delbert E. Gantz Assistant E.\'aminerG. E.Schmitkons Anorneys- Pearlman and Stahl and N, Elton Dry ABSTRACT:lmproved catalysts for the selective conversion of straight-chainhydrocarbons contained in a hydrocarbon feed comprise a synthetic,relatively small pore size crystalline alumino-silicate zeolite.Preferably, the synthetic small pore size zeolite is combined with ametallic hydrogenation component and used in the selective conversion oflow octaneproducing normal paraffins to upgrade the hydrocarbon feedstock. The process is preferably conducted in the presence of addedhydrogen at elevated temperatures and pressures.

CATALYSTS FOR THE SELECTIVE CONVERSION OF STRAIGHT-CHAIN HYDROCARBONSCROSS-REFERENCES TO RELATED APPLICATIONS This case is acontinuation-in-part of U.S. Ser. No. 667,660, filed Sept. 14, 1967 (nowU.S. Pat. No. 3,575,846) and U.S. Ser. No. 637,911, filed May 12, 1967,now U.S. Pat. No. 3,497,448.

BACKGROUND OF THE INVENTION 1. Field ofthc Invention This inventionrelates to the removal of straight-chain hydrocarbons from hydrocarbonfeedstocks containing same in combination with nonstraight-chainhydrocarbons. More particularly, it relates to the use of an improvedcatalyst for this purpose, which catalyst comprises a relatively smallpore size crystalline alumino-silicate zeolite which has beensynthetically prepared. Still more particularly, it relates to aselective hydrocracking process accomplished in the presence of asynthetic, small pore size crystalline zeolite having a low alkali metalcontent, and combined with a metallic hydrogenation component, saidprocess being conducted with the imposition of a substantial hydrogenpressure. In its most preferred aspects, the invention relates to theoctane improvement of naphtha feeds using the above-described process,particularly in connection with conventional reforming operationswherein the aforedescribed catalyst can be used either before, during orafter the reforming operation so as to remove the low octane-producingstraight-chain components of the petroleum-derived feed and/or product.

2. Description of the Prior Art Hydrocarbon conversion and upgradingwith crystalline alumino-silicate zeolite catalysts are now well knownin the art. The use of these materials for such purposes ashydrocracking has been generally directed to typical petroleumderivedfeedstocks such as gas oils, etc., which are customarily converted tolower boiling products useful as gasoline. The crystalline zeolitesemployed for such purposes usually have uniform pore openings of about 6to 15 angstroms and are therefore nonselective; that is, substantiallyall of the feed molecules are admitted into the zeolite pore structureand converted. For many purposes selective hydrocracking of particularmolecular species in the feed to the substantial exclusion of others isdesired. For example, octane improvement of naphtha fractions can beaccomplished by selectively hydrocracking only. the straight-chainhydrocarbons (e.g., olefins, paraffins, etc.) which-tend to be lowoctane-producing, thereafter removing the hydrocracked products, andfinally recovering a higher octane product. Selective hydrocracking ofstraight-chain hydrocarbons contained in lube oil or gas oil fractionsis also valuable for the purpose of pour point reduction or dewaxing.

The use of a nonselective large pore (eg 6 to 15 angstroms) crystallinezeolite for such purpose is largely ineffectual, as the desired feedmolecules (e.g. aromatics) are admitted into the zeolite pores andconverted together with the straight-chain hydrocarbons. it has now beenfound that certain specific small pore size zeolites provide a valuableand unique catalyst component for the selective hydrocracking ofstraight-chain hydrocarbons. The zeolites specifically are those smallpore size crystalline zeolites which have been synthetically produced.and which further have a low alkali metal content.

By relatively small pore size" is meant a pore size of below about 6angstrom units. particularly 4 to 6 angstroms e.g. about 5 angstroms.More particularly, the catalyst employed will have pores capable ofaffording entry to the objectionable normal paraffinic hydrocarbons butincapable of admitting the more valuable branched and cyclichydrocarbons. For convenience, these materials may hereinafter bereferred to generally as S-angstrom zeolites." The result of suchtreatment is to selectively convert the normal paraffmic componentseither to lower boiling saturated products which can then be readilyremoved, thereby leaving a naphtha product of highly improved quality,or to desirable branched-chain paraffins and/or olefins which tend to behigh-octane-producing components.

The synthetic preparation of crystalline metalloalumino-silicatezeolites having uniform pore openings of less than about 6 angstromscontemplated for use in this invention is well known. Basically, itinvolves crystallization from reaction mixtures containing suitablesources of alkali metal oxide, silica, alumina and water. The proportionof the various ingredients will determine the type of synthetic zeoliteobtained, as well as its crystallinity and the yield of final product.However, it will be appreciated that for any particular type ofcrystalline zeolite a wide range of reactant ratios can be employed withvarying degrees of success.

The sources of the various ingredients mentioned above may vary, but arepresentative list for each would include; 1 as a source of silica:sodium meta silicate, sodium polymeric silicate, silica gel, silicasol., with silica sol. being particularly preferred; (2) as a source ofalumina: sodium aluminate, alumina sol., alumina-trihydrate, aluminumsalts of organic and inorganic acids such as aluminum acetate, aluminumchloride, aluminum sulfate and the like, with sodium aluminate beingparticularly preferred; and (3) as a source of alkali metal oxide:sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium oxide,potassium oxide, cesium oxide, potassium aluminate, potassium silicatewith the hydroxides of sodium and potassium being particularlypreferred. In the synthesis of certain zeolites, such as erionite, acombination of such sources of alkali metal oxides, such as acombination of sources of sodium and potassium, is required.

In order to achieve a particularly desired result, a judicious selectionof reactant ratios, crystallization times, reactant source materials andprocess conditions are required. Generally, for the production of thesmall pore size zeolite erionite, the reactants are thoroughly mixed atambient temperatures, heated to a temperature of from about to 150 C.,preferably to C., and held at such a temperature for a sufiicient periodof time to form the crystalline zeolite product, preferably from 1 to 10days, and most preferably from 2 to 6 days. The pressure utilized willusually be about atmospheric pressure in the case of operation at orbelow 100 C., and will be correspondingly increased to the vaporpressure of the reaction mixture at a temperature higher than 100 C., inorder to prevent substantial loss of water from the reaction mixture.Typical optimum crystallization times for temperatures from 80 to 1 10C. will be about 50 to about 300 hours, preferably from 100 to 200hours. Higher temperatures will allow shorter crystallization times.

For temperatures in the vicinity of 147 C., for example, suitablecrystallization periods will usually range from about 1 to 3 days,preferably 1.5 to 2 days. After the formation of the crystalline zeolitephase, the zeolite crystals are filtered from the mother liquor andpreferably washed throughout until the water wash has a pH of about 8 tol 1. Afterwards, the zeolite crystals are preferably dried in air at atemperature, for example, of about 100 to 200 C. The crystals may befinally activated for use as an absorbent or as a catalyst support byheating at a temperature of about 250 to 350 C. to thereby drive offwater of hydration, leaving a crystalline structure interlaced withcanals of molecular dimensions.

Specifically, the relatively small pore size synthetic zeolites of thepresent invention include the synthetic counterparts of the naturallyoccurring zeolites erionite, chabazite and analcite. The most preferredzeolite being erionite. The preparation of the small pore size syntheticzeolites erionite is, basically, as follows:

Reaetant mole ratios Particularly Erionite per se is a naturallyoccuring zeolite having elliptical pore openings of about 4.7 to 5.2angstroms on its major axis. The synthetic counterpart has beendesignated in the art as Zeolite T in US. Pat. No. 2,950,952, and ischaracterized by a stoichiometric composition, in terms of mole ratiosof ox-' SUMMARY OF THE INVENTION It is a primary object of the presentinvention to provide a catalyst of improved activity for use in theselective conversion of straight-chain hydrocarbons contained inadmixture with nonstraight-chain hydrocarbons.

In accordance with the present invention it has now been discovered thatcertain small pore size crystalline alumino-silicate zeolites exhibitsuperior activity when used as catalysts to selectively convertstraight-chain hydrocarbons from a mixture of hydrocarbons of variousconfiguration. In particular, it has been found that syntheticallyprepared crystalline alumino-silicates, having a uniform pore size ofless than about angstroms, particularly those which represent thesynthetic counterparts of certain naturally occurring small pore sizecrystalline zeolites, exhibit such superior catalytic activity,particularly when compared with their naturally occurring counterparts.These catalysts of the present invention will find their highest utilityin the process of selectively hydrocracking straight chain components ina hydrocarbon feed stock, particularly a naphtha feed stock, eitherprior to or subsequent to conventional reforming operations.

DETAILED DESCRIPTION The starting materials for the preparation of thecatalysts of the present invention are the synthetically producedrelatively small pore size crystalline alumino-silicate zeolitesdescribed above.

These small pore size synthetic zeolites are treated to removeessentially all of the sodium alkali metal content and a substantialamount of the potassium alkali metal content. Prior to alkali metalremoval, these small pore size zeolites generally have an alkali metalscontent in the range of about 8.5 to ID weight percent. Conventionalmeans for reducing the alkali metal content, such as by ion exchangewith a replacing cation. will ordinarily be sufficient to reduce thepotassium content by about 40 percent, e.g. down to a level of about 5.0to 6.5 weight percent. In order to further reduce this level, variousmeans are provided. This additional alkali metal removal has thesurprising effect of increasing its activity (i.e. operation at a lowertemperature produces equivalent results) and the selective conversionability of the zeolite material, so as to remarkably enhance its utilityas a catalyst for the selective conversion of straight-chainhydrocarbons. Two of the most convenient means involve either the use ofhigh temperatures in the ion exchange with a suitable solutioncontaining a replacement cation, or multiple exchanges with two or moredifferent types of replacement cations which has the effect of reducingthe potassium ion content to a greater degree than possible through theuse of only one replacement cation. By these procedures, final alkalimetal levels below 3.5 weight percent, and preferably below 1.5 weightpercent may be obtained.

It has'been found that conventional ion exchange with certain cationsolutions at high temperatures will accomplish the desired degree ofalkali metal reduction. In this connection it will be necessary toconduct the ion exchange at temperatures in the range of about 150 to300 F., preferably 180 to 225 ;F., and it will be further necessary toconduct multiple exchanges with the cationic solution. Generally, atleast two exchanges and preferably three exchanges will be required toachieve the desired degree of reduction. In addition to the 0temperature at which the exchanges are conducted, it has .been foundthat the type of cation and anion present in the exchange solution willhave an effect on the degree of reduction attainable. Suitable cationswill include hydrogen, ammonium, sodium, magnesium, zinc, and calciumcations. Suitable anions will include nitrate, sulfate, chloride andacetate anions. Of these, combinations of (l hydrogen cation with eitherthe nitrate, chloride or sulfate anions (acid solutions); and (2)ammonium cation with one of the aforementioned anions, are consideredmost effective in reducing the potassium content. With these acidicsolutions, concentrations should be maintained at low levels to preventdeterioration of the crystal structure. Thus, for example, withsolutions of hydrochloric and nitric the solution is maintained at lessthan 1 normal. While some replacement of the alkali metal with themetallic cations does occur, it is to a lesser degree than with thehydrogen or ammonium cations.

A second means for reducing the alkali metal content to the desiredranges involves the use of multiple cation exchange at "ambienttemperature using hydrogen-containing cation solutions and metalcation-containing solutions. By initial exchange of the zeolite withhydrogen-containing cations followed by exchange with metal cations, thelow alkali metal levels can be achieved. In this multiple ion exchangetreatment the zeolite will preferably be first treated under highlyacidic conditions, eg a pH of l-5 with an acid or a solution of a saltof a weak base and a strong acid. Ammonium salts of hydrochloric,nitric, and sulfuric acid are particularly suited for this purpose. Theinitial hydrogen and/or ammonium ion exchange will usually be sufficientto reduce the potassium content by about 50 to 70 percent, i.e. down topotassium levels of about 2 to 3.5 weight percent of the erionite.Following this initial ammonium or hydrogen ion treatment, furtherreduction in potassium content is accomplished by exchange with ametallic cation. Typical metallic cations will include cations of metalsin Groups IA, IB, IIA, IIB, VIIB and VIII, particularly IB, IIB, andVIII and most particularly metals in Group IIB of the Periodic Table,e.g., zinc and cadmium. This second ion exchange treatment willusuallybe sufficient to further reduce the alkali metal content by about50 to per cent, i.e. down to levels of about 0.5 to 3.0 weight percentof the zeolite.

A final minor reduction in alkali metal content is achieved byincorporation of a hydrogenation component. This last step reduction inpotassium is comparatively small. In the case of those catalystsprepared by use of ammonia complexes and ammoniacal solutions of metalssuch as platinum group metals, this final increment removal may beconsidered as an additional ammonium ion exchange; although at thedilutions usually employed it is essentially an additional wash stepserving to remove the potassium ions displaced by the metal ionexchange.

The exchanges involve contact of the zeolite, with stirring, withaqueous solutions containing the exchanging ion in concentrationsranging from about 5 to 30 weight percent concentration, preferably 10to 25 weight percent concentration for periods ranging from 1 to 30hours, preferably 2 to 6 hours. The preferred exchange techniqueinvolves suspension of the zeolite in water and addition of aconcentrated solution thereto with good agitation so that the resultantconcentration of the exchange ion falls within preferred ranges.Following the exchange and removal of the contacting solution byfiltration the cake is water washed by suspension, with good agitationin typical proportions of about one to 10 parts by weight of water fromtypical periods of 0.5 to 2, e.g., about 1 hour. In

the case of ammonium and zinc ion exchanges (moderately acidicsolutions) is is desired that all contact with treating solution andwashes be at ambient temperature to avoid losses of crystallization. Thecatalysts discussed subsequently and prepared by multiple ion exchangeswere water washed one time after each exchange and three times after thelast exchange.

As a further step in the preparation of the catalysts of the invention,the catalyst is preferably combined with an active metallichydrogenation component which may be chosen from Groups VB, VlB, VllB orVIII of the Periodic Table and which is suitably exemplified by themetals cobalt, platinum, chromium, palladium, molybdenum, tungsten, etc.The hydrogenation component may be in the form of the free metal as inthe case of platinum group metals, or as the oxide or sulfide as in thecase of cobalt, etc., or mixtures of such metals, oxides or sulfides.Platinum group metals'(i.e. metals of the platinum and palladium series)will be preferred for purposes of the present invention, with palladiumbeing particularly preferred. In addition, the nonnoble metals of GroupVIII are also particularly preferred for use as active hydrogenationcomponents. These include nickel, cobalt, iron, with nickel particularlypreferred, and additionally to which the oxy and/or the anion of GroupVl metals, including molybdenum and tungsten may be adducted.Incorporation of the hydrogenation component may be accomplished by anyconventional technique such as ion exchange followed by reduction,impregnation, etc. When palladium is employed, the zeolite is preferablyimpregnated with an ammoniacal solution of palladium chloride sufficientto produce the desired amount of hydrogenation metal in the finalproduct, and then dried and calcined at a temperature of 800 to l000 F.Reduction of the metal is then accomplished either separately or in thehydrocracking reaction per se. The amount of hydrogenation component mayrange from about 0.1 to about 25 weight percent, preferably about 2 toabout weight percent, based on the weight of final product. In the caseof platinum group metals, e.g. palladium, the preferred amount will bein the range of about 0.1 to 6 e.g., 0.5 to 3 weight percent based ondry catalyst. ln the case of the nonnoble metals of Group Vlll, where aGroup V] anion is adducted thereto, the preferred combination will benickel-tungsten, wherein the nickel is present in the range of from 2 to5 weight percent, and the tungsten, as the oxide, is present in therange of from 4 to 10 weight percent.

It has been further found that the activity and effectiveness of certaincatalysts used herein may be substantially improved by contact withsulfur prior to or during their use in the selective hydrocrackingprocess. Specifically, those catalysts of the invention wherein thesynthetic zeolite has been exchanged with Group "-8 metal cations, areparticularly susceptible to improvement via sulfactivation. The catalystis preferably sulfactivated in these instances to enhance its activityby contact either with a sulfur-containing feed, or if the feed has alow sulfur content, with hydrogen sulfide or an added sulfur compoundwhich is readily convertible to hydrogen sulfide at the hydro conditionsemployed, e.g., carbon disulfide, etc. The extent of this sulfactivationtreatment should be sufficient to incorporate 0.5 to l5 weight percentsulfur into the catalyst.

The feed stocks utilized in the present invention will generally includemixtures of hydrocarbons and particularly petroleum distillates fallingwithin the approximate range of about 80 to about 850 F which range willinclude naphthas, gasolines, kerosenes, gas oils, middle distillates,etc. Preferably, the feed will be predominantly naphtha-containing andmay consist of either low boiling or high boiling naphthas. Typical lowboiling feeds will have boiling ranges of about 50 to 350 F., preferably75 to 300 F whereas typical heavy naphtha feeds will boil within therange of about 250 to 450 F preferably 300 to 430 F. Examples of suchfeed stocks both low boiling and high boiling, are virgin naphthafractions such as C -C naphtha, heavy virgin naphtha, heavy cokernaphtha, heavy steam cracked naphtha, heavy catalytic naphtha, etc.Particularly preferred feed stocks will include the light naphthas asdescribed above, naphthas suitable as hydroformer feeds and naphthaproducts from the hydroforming operation, which feeds will typicallyboil in the range of about 50 to 400 F., preferably to 350 F. A primehydroformer feed will have about a 180 to 360 F. boiling range. Arequirement for the feed stocks used in the present invention is thatthey contain a substantial quantity of straight chain hydrocarbons whichare converted or removed in accordance with the present invention.

The above feed stocks are treated with the aforedescribed small poresize synthetic zeolite catalysts in either fixed bed, moving bed, orfluidized solids operation, either upflow or downfiow (in bed reactors),at the following operating conditions:

Generally Particularly Kerosene-gas oil of 300860 F. boiling range.

2 Naphthas of 50200 F. boiling range.

Naphthas in 180-430" F. boiling range usable in hydroforming operations.

The essence of the present invention, namely the use of theaforedescribed catalysts for the selective removal of straightchainhydrocarbons, can be utilized in various processing schemes dependingupon the results desired. These various processing schemes will not bedescribed in some detail as they represent specific embodiments of thepresent invention.

The catalysts of the invention can conveniently be used to upgradenaphtha fractions for inclusion in the high-quality motor gasolinepools. This may involve a single-stage operation wherein the naphthafeed is introduced into contact with the synthetic small pore sizecatalysts at the aforedescribed conditions and the resulting product hasa greatly enhanced octane number.

The zeolite catalysts of the invention can be utilized to upgradepreviously hydrocracked feed stocks, e.g. an additional hydrocrackingstage containing small pore size synthetic zeolite catalysts can be usedin conjunction with a conventional hydrocracking operation in order toproduce a higher octane product. The conventional hydrocracking stagesare conducted with any of the various available hydrocracking catalystsand most preferably with the newly developed relatively large pore size(e.g. 6 to 15 angstrom units) crystalline alumino-silicate zeolitecatalysts containing metallic hydrogenation components. Such catalystshave been extensively described in the prior art, e.g. U.S. Pat. Nos.2,971,904 and 3,287,252. In this embodiment the total hydrocrackedproduct from the relatively large pore size zeolite catalysts, or aselected portion thereof, may be contacted with the selective small poresize, synthetic catalysts of the invention. intermediate fractionationand segregation of desired fractions can be used. Typical hydrocrackingconditions with the large pore zeolite catalysts will includetemperatures from about 400 to 800 F., pressures of about 250 to 2,500p.s.i.g. liquid hourly spaced velocities of about 0.2 to 5 V/V hr. andhydrogen ranges of about 1,000 to 20,000 s.s.f./bbl.

The synthetic zeolite catalysts of the present invention can be used inconjunction with conventional hydroforming operations. in this case thezeolite catalysts can be used in a lead reactor to pretreat the feedpassing to the hydroforming reactors, or can be utilized either in aseparate tail reactor or in a bottom portion of the last reactor of theseries employed in a hydroformer, to selectively convert the remainingstraight-chain hydrocarbons so as to further increase the octane numberhydroforrned product. The catalysts can also be utilized in admixturewith conventional hydroforming catalysts in one or more conventionalhydroforming reactors.

Hydroforming operations are well known in the art and involve treatmentof hydrocarbon fractions boiling in the motor fuel or naphtha range atelevated temperatures and pressures in the presence of certain solidcatalysts and hydrogen. Hydroforming usually consists of treatinghydrocarbon. vapors in the presence of hydrogen or a hydrogen-rich gasat typical temperatures of 850 to 1,000 F. and pressures of 50 to 1,000p.s.i.g. with catalysts such as the oxides or sulfides or metals ofGroups IV, V, VI, VII and VIII of the Periodic Table, either alone orpreferably supported on suitable relatively large pore size base such asalumina gel, precipitated alumina, zinc alumina, silica alumina, etc.Typical hydroforming catalysts include the oxide Group VI metals such asmolybdenum, chromium, the metals of the palladium series such asplatinum, palladium etc. deposited on a suitable support such asalumina, silica-alumina or components thereof. These catalysts maycontain varying amounts of halogen, boria, or other components designedto enhance their activity or selectivity. A particularly suitablecatalyst of the art comprises platinum (e.g. 0.02 to 2.0 weight percent)on alumina containing a minor amount (e.g. 0.1 to 0.5 weight percent) ofa chloride or fluoride.

The hydroformed product stream (hydroformate) from a typicalhydroforming operation will usually contain a substantial portion (e.g.l to 15 weight percent) of normal paraffinic hydrocarbons having anundesirably low octane rating. As such hydroformate streams representexcellent candidates for upgrading by means of the present inventionwith the low alkali metal content synthetic zeolite catalyst. This isaccomplished by contacting refonned naphtha stream in the presence ofgaseous hydrogen which may be either separately added or, morepreferably, included in the reformer gas with a catalyst of the typehereinbefore described. The result of such treatment is to selectivelyconvert the normal paraffimic components to lower boiling saturatedproducts which can be readily recovered, thus leaving a naphtha productof greatly enhanced quality. A number of conventional hydroformingstages can be employed prior to the final treatment with the catalyst ofthe invention. Moreover, the entire hydroformate can be subjected to thesmall pore size synthetic zeolite catalyst, or a selected portionthereof can be thus treated. Further, a selective fraction of thehydroformate can be separated by, for example, fractionation, saidfraction containing a high proportion of the undesirable straight-chainhydrocarbons, and this fraction separately contacted with the small poresize synthetic zeolite catalysts so as to upgrade it, followed byblending back with the remainder of the hydroformate to achieve anoverall increase in octane rating without necessity for subjecting theentire hydroformate to the small pore size synthetic zeolite catalyst.

As mentioned, it is additionally contemplated to pretreat a typicalhydroformer feed stock, such as a virgin naphtha, prior to its contactwith the conventional hydroforming catalysts of the art. The selectiveconversion of the undesirable straightchain component in the feed leavesthe desirable naphthenic and aromatic portions essentially unchanged. Inthe hydroforming zones per se, less carbon formation will beencountered. Subsequent to the pretreatment stage, any number ofconventional hydroforming stages can be employed, The hydroformateproduced may be blended with a high-octane C,and C product from thepretreatment zone separated in a fractionation zone to thereby obtainmaximum yield of high octane products. Further, the hydroformate itselfcan be separated by fractionation with subsequent recovery and blendingof the higher octane fractions for particular uses or purposes.

As mentioned, in addition to the posttreatment and pretreatment ofhydroformer feed stocks and products asjust described. it is furthercontemplated that the zeolite catalyst can be uniformly admixed with theconventional hydroforming catalysts to achieve the desirable resultsherein described. These include conversion of normal paraffins togaseous hydrocarbons simultaneously with the dehydrogenation reactionsto produce aromatics. The aromatics so produced are predominantlybenzene and toluene because of the dealkylation properties of theerionite in the reformer reactors. Thus, upon comingling theconventional hydroformer catalyst and the small pore size syntheticzeolite catalysts, there results a product predominately comprised oflower boiling aromatics and which is essentially normal paraffin free.These improvements are reflected in a higher octane number naphtha. Theproducts boiling lower than the desired naphtha range, e.g. C areremoved by distillation.

Finally, as also mentioned, it is further contemplated that the tailreactor of a conventional hydroforming operation will contain syntheticzeolite catalyst in the last increment of reactor space, asdistinguished from an entirely separate reactor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Product wt. Distribution.

C, and lighter L8 iso-penlane l4.l normal-penlanc 24.2 ism-hexane 30.9normal-hexane 22.9

benzene and methyl cyclnpcntanc 6.]

The superior activity of a synthetic zeolite catalyst as compared to itsnaturally occurring counterpart is illustrated with this feed, utilizinga palladium hydrogen erionite catalyst, as follows:

HYDROSELECTIVE CRACKING OF ARABIAN C0-C6 NAPII- .THA.SYNTHETIC vs.NATURAL ERIONITE AS CATA- LYST COMPONENT Feed rate=0.6 v./v./hr., 500p.s.i.g., 1,600-3,000 s.c.i./b. II; gas rate] Palladium hydrogenerionite catalysts:

Preparation A B Erionite S0urce.. Synthetic Natural Potassium contentalyst, wt. percent 3. 7 8. 7

Temperature, F 760 700 750 700 Analytical data on liq. prod.:

n-C wt. percent 0. 9 2. 0 10.2 12. 7

n-C; wt. percent 0. 2 0. 3 2. 6 4. 4 Conversion of feed to Cl 73 62 4236 HYDROSELECTIVE CRACKING OF ARABIAN C5-C5 NAIII- THA.-SYNTHETIC vs.NATURAL ERIONIIE AS CATA- LYS'I COMPOUND [Feed rate QB v./v./hr., 500p.s.i.g., i,500-3,000 s.c.1./b. II: gas rate] Palladium zinc erionitecatalysts:

Preparation C I) Erionite source Synthetic Natural Potassium content ofcatalyst, wt. percent... .5 3. 2 Temperature, F 750 850 750 Analyticaldata on liq. prod.:

n-Cs, wt. percent 0.1 1. 2 1.7 5. 4

n-Ct, wt. percent 0.0 0. 1 0.7 2. 6 Conversion of feed to C4, wt.percent 72 61 62 49 9 Example 3 This example illustrates the advantageof the synthetic base for a zinc-palladium catalyst when processing areformate feed for normal paraffin conversion, and to thus achieve aproduct An added advantage of the synthetic zeolite is that control ofsynthesis conditions will lead to constant performance. This is not tobe expected with the naturally occurring zeolites where variations inconditions of formation, secondary having an improved octane rating. 5exchanges and dilution with extraneous material lead to variation inperformance. Variable performance when synthesis conditions are out ofcontrol is illustrated with catalysts from HYDROSELECTIV E CRACKING FREFORMATE.SYN- the naturally occurring erionites as follows:

THETIC Vs. NATURAL ERIONIIE AS CATALYST COM- PONENT l HYDROSELECTIVECRACKING 0F ARABIAN 06-0 [Feed rate B v./v./hr., 500 p.s.l.g.,1,0002,000 s.c.t.lb. Hr gas rate] A P Zn CA ALY FROM NATURALLY OCCURRINGERIONITES Palladium zinc erlonite catalysts (presulfided):

gixgigliatgilifi: n: y g Nagml [0.5 v./v./hr. at 500 p.s-i.g.,1,5003,000 s.c.f./b. H: gas rate] Temperature 7 F- Preparation E F DErionite Source Pine Valley, Rome, Not iden- Analytical data on liquidproduct: Nevada Oregon tified n-Paraffins, wt. percent I O. 16 1. 65Percent removal 97 67 Temperature, F 800 750 850 750 850 760 Octanes:Analytical date on liq. prod;

RON clear 1.9 101-5 Wt. percent n-C 1.9 4.7 10.7 14.2 1.7 6.4 MON clear1 90. 8 0- 4 wt. percent n-ct... 9.1 0.4 5. s 14.1 0. 7 2. 6 Feed: 4.74.2 Feed: 995 a F e 88.0. 20 Conversion of feed to 04. 63.2 66.7 41.8 20.962.3 49. 2

From the conversion-temperature relationship. preparation The syntheticerionite base catalyst shows l0 fold better E is somewhat more activethan preparation D and either of normal paraffin removal at equivalentprocess conditions and the two is markedly superior to preparation F.Such variations thus a higher research and motor octane value for theliquid would not be expected in a synthetic base with reactioncondiproduct. tions under control and where extraneous impurities aremain- Example 4 tained at a minimum. This example illustrates theeffectiveness of a synthetic What is claimed is: erionite basezinc-palladium catalyst (sulfided) for hydrodeal- 1. An improved processfor selectively removing straightkylation of C, to C aromatics tobenzene and toluene. chain hydrocarbons from a hydrocarbon feed whichcom- HYDROSELECTIVE CRACKING 0F HEAVIER AROMATICS Pris?s Selectivelyhydtocl'acking Said feed y Contact, at m REFORMATE elevated temperatureand pressure and in the presence of h dro en, with a catalyst com risina s nthetic cr stalline [Feed 600 2'000 gas rate 950 al iimisosilicatezeolite having the stfuctui' e of erioni te, said Palladium-zin rlonitlyst (sul (p 1 zeolite further having a relatively small pore size, analkali aration C) Feed Product metal content of less than about 3.5weight percent, and being Composition, percenti combined with a metallichydrogenation component.

Benzene 21K 2. The process of claim 1, wherein said metal in said metal-3 40 lic hydrogenation component comprises a metal selected from 99 6the group consisting of metals in Groups V-B, Vl-B, Vll-B and 5 3 VIIIof the Periodic TAble. r 3. The process of claim 1, wherein saidhydrogenation com- Benzene yield is increased 4.7 fold and tolueneincreased ponent comprisesaplatinum group metal. 1.5 fold even thoughthe reformate was essentially free of 4. The process of claim 1 whereinsaid zeolite has been canaphthenes. The octane improvement may beattributed to tion-exchanged at a temperature within the range of aboutnormal paraffin conversion to gaseous products and the deal- 150 to 300F. kylation of ethyl benzene and other higher aromatics to 5. Theprocess of claim 1, wherein said zeolite has been base benzene andtoluene. exchanged with hydrogen-containing cations.

Example 5 6. The process of claim 1, wherein said zeolite has been ca-This example illustrated the utility of Palladium Hydrogention-exchanged with both hydrogen-containing cations and Erionite(synthetic) for improving the octane sensitivity of metal cations.olefinic catalytic naphtha (hydrotreated). 7. The process of claim 1,wherein said zeolite has been cation-exchanged with Group "-8 metalcations. I 8. The process of claim 1, wherein the alkali metal contentHYDROSELEOTIVE CRACKING OF LIGHT CATALYTIC of said zeolite is less thanabout 2.6 weight percent.

gg figgggg ERIONITE AS CATALYST 9. The process of claim 1, wherein thealkali metal content of said zeolite is less than about 1.5 weightpercent. Bed r8te=1 -l -l n, 600 D i-g 2,000 s.c.f. Hll 8 rate. F -l 10.The process of claim 1, wherein said hydrocarbon feed Hydrogen palladiumerionite catalyst (preparation A) is predominantly naphtha containing yr in yr iv 11. The process of claim 1, wherein said feed comprises a ffg hydroformed naphtha product stream. 8 y agg gg ggg fisg i ggge h(1126: lprgcess of claim 1, wherein said feed is a previously tabillzednaphtha inspections Feed product product y C e S cam o 13. The catalystcomposition comprising a metallic 3:3 am 3 3 5 2: 1,3 hydrogenationcomponent combined with a relatively small Sulfur, p.p.m 330 47 poresize synthetic crystalline alumino-silicate zeolite, said Octane data:

ROM plus 3 cc. 'IEL 99 953 7 zeolite having an alkali metal contentlower than that attaina- MON plus 3 cc. TEL 86 91. 3 93. 6 ble by cationexchange at relatively low temperature. Octane sensitivity 13 4 6 70 14.The composition of claim 13, wherein the alkali metal is less than about4 weight percent.

15. The composition of claim 13, wherein the alkali metal Superioroctane product of less sensitivity is obtained by content is less thanabout 2.6 weight percent. hydroselective cracking of a light catalyticnaphtha. 16. The composition of claim 13, wherein the alkali metalcontent is less than about 1.5 weight percent.

Example 6 Disclaimer 3,625,880.--Glen P. Hamnew, Baton Rouge and RalphB. Mason, Denham Springs, La. CATALYSTS FOR THE SELECTIVE CONVER- SIONOF STRAIGHT-CHAIN HYDROCARBONS. Patent dated Dec. 7 1971. Disclaimerfiled June 11, 1971, by the inventors; the assignee, Essa Research andEngineering Company, assenting. Hereby disclaims the portion of the termof the patent subsequent to Apr. 20, 1988.

[Ofiiez'al Gazette September 19, 1.972.]

2. The process of claim 1, wherein said metAl in said metallichydrogenation component comprises a metal selected from the groupconsisting of metals in Groups V-B, VI-B, VII-B and VIII of the PeriodicTAble.
 3. The process of claim 1, wherein said hydrogenation componentcomprises a platinum group metal.
 4. The process of claim 1 wherein saidzeolite has been cation-exchanged at a temperature within the range ofabout 150* to 300* F.
 5. The process of claim 1, wherein said zeolitehas been base exchanged with hydrogen-containing cations.
 6. The processof claim 1, wherein said zeolite has been cation-exchanged with bothhydrogen-containing cations and metal cations.
 7. The process of claim1, wherein said zeolite has been cation-exchanged with Group II-B metalcations.
 8. The process of claim 1, wherein the alkali metal content ofsaid zeolite is less than about 2.6 weight percent.
 9. The process ofclaim 1, wherein the alkali metal content of said zeolite is less thanabout 1.5 weight percent.
 10. The process of claim 1, wherein saidhydrocarbon feed is predominantly naphtha containing.
 11. The process ofclaim 1, wherein said feed comprises a hydroformed naphtha productstream.
 12. The process of claim 1, wherein said feed is a previouslyhydrocracked stream.
 13. The catalyst composition comprising a metallichydrogenation component combined with a relatively small pore sizesynthetic crystalline alumino-silicate zeolite, said zeolite having analkali metal content lower than that attainable by cation exchange atrelatively low temperature.
 14. The composition of claim 13, wherein thealkali metal is less than about 4 weight percent.
 15. The composition ofclaim 13, wherein the alkali metal content is less than about 2.6 weightpercent.
 16. The composition of claim 13, wherein the alkali metalcontent is less than about 1.5 weight percent.